/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

var zrUtil = require("static/plugins/js/zrender/lib/core/util");

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

/* global Uint8ClampedArray */
var GRADIENT_LEVELS = 256;
/**
 * Heatmap Chart
 *
 * @class
 */

function Heatmap() {
    var canvas = zrUtil.createCanvas();
    this.canvas = canvas;
    this.blurSize = 30;
    this.pointSize = 20;
    this.maxOpacity = 1;
    this.minOpacity = 0;
    this._gradientPixels = {};
}

Heatmap.prototype = {
    /**
     * Renders Heatmap and returns the rendered canvas
     * @param {Array} data array of data, each has x, y, value
     * @param {number} width canvas width
     * @param {number} height canvas height
     */
    update: function (data, width, height, normalize, colorFunc, isInRange) {
        var brush = this._getBrush();

        var gradientInRange = this._getGradient(data, colorFunc, "inRange");

        var gradientOutOfRange = this._getGradient(
            data,
            colorFunc,
            "outOfRange"
        );

        var r = this.pointSize + this.blurSize;
        var canvas = this.canvas;
        var ctx = canvas.getContext("2d");
        var len = data.length;
        canvas.width = width;
        canvas.height = height;

        for (var i = 0; i < len; ++i) {
            var p = data[i];
            var x = p[0];
            var y = p[1];
            var value = p[2]; // calculate alpha using value

            var alpha = normalize(value); // draw with the circle brush with alpha

            ctx.globalAlpha = alpha;
            ctx.drawImage(brush, x - r, y - r);
        }

        if (!canvas.width || !canvas.height) {
            // Avoid "Uncaught DOMException: Failed to execute 'getImageData' on
            // 'CanvasRenderingContext2D': The source height is 0."
            return canvas;
        } // colorize the canvas using alpha value and set with gradient

        var imageData = ctx.getImageData(0, 0, canvas.width, canvas.height);
        var pixels = imageData.data;
        var offset = 0;
        var pixelLen = pixels.length;
        var minOpacity = this.minOpacity;
        var maxOpacity = this.maxOpacity;
        var diffOpacity = maxOpacity - minOpacity;

        while (offset < pixelLen) {
            var alpha = pixels[offset + 3] / 256;
            var gradientOffset = Math.floor(alpha * (GRADIENT_LEVELS - 1)) * 4; // Simple optimize to ignore the empty data

            if (alpha > 0) {
                var gradient = isInRange(alpha)
                    ? gradientInRange
                    : gradientOutOfRange; // Any alpha > 0 will be mapped to [minOpacity, maxOpacity]

                alpha > 0 && (alpha = alpha * diffOpacity + minOpacity);
                pixels[offset++] = gradient[gradientOffset];
                pixels[offset++] = gradient[gradientOffset + 1];
                pixels[offset++] = gradient[gradientOffset + 2];
                pixels[offset++] = gradient[gradientOffset + 3] * alpha * 256;
            } else {
                offset += 4;
            }
        }

        ctx.putImageData(imageData, 0, 0);
        return canvas;
    },

    /**
     * get canvas of a black circle brush used for canvas to draw later
     * @private
     * @returns {Object} circle brush canvas
     */
    _getBrush: function () {
        var brushCanvas =
            this._brushCanvas || (this._brushCanvas = zrUtil.createCanvas()); // set brush size

        var r = this.pointSize + this.blurSize;
        var d = r * 2;
        brushCanvas.width = d;
        brushCanvas.height = d;
        var ctx = brushCanvas.getContext("2d");
        ctx.clearRect(0, 0, d, d); // in order to render shadow without the distinct circle,
        // draw the distinct circle in an invisible place,
        // and use shadowOffset to draw shadow in the center of the canvas

        ctx.shadowOffsetX = d;
        ctx.shadowBlur = this.blurSize; // draw the shadow in black, and use alpha and shadow blur to generate
        // color in color map

        ctx.shadowColor = "#000"; // draw circle in the left to the canvas

        ctx.beginPath();
        ctx.arc(-r, r, this.pointSize, 0, Math.PI * 2, true);
        ctx.closePath();
        ctx.fill();
        return brushCanvas;
    },

    /**
     * get gradient color map
     * @private
     */
    _getGradient: function (data, colorFunc, state) {
        var gradientPixels = this._gradientPixels;
        var pixelsSingleState =
            gradientPixels[state] ||
            (gradientPixels[state] = new Uint8ClampedArray(256 * 4));
        var color = [0, 0, 0, 0];
        var off = 0;

        for (var i = 0; i < 256; i++) {
            colorFunc[state](i / 255, true, color);
            pixelsSingleState[off++] = color[0];
            pixelsSingleState[off++] = color[1];
            pixelsSingleState[off++] = color[2];
            pixelsSingleState[off++] = color[3];
        }

        return pixelsSingleState;
    },
};
var _default = Heatmap;
module.exports = _default;
